Corrective glasses typically have lenses that have been ground or otherwise formed to provide refraction according to a prescription particular to the user. Typically, refractive lenses are mounted in a frame which encircles each of the two lenses and extends to the ears for support.
Bifocal lenses are ground or formed to accommodate two different refractive characteristics at two locations within one lens. Typically, as a person ages, his or her eyes lose elasticity and are unable to focus at close ranges as they once did. Bifocals have two areas of different refractive characteristics so that an area providing relatively great magnifications permits the user to undertake activities such as reading, while the rest of the lens is directed to more distant visual tasks.
From time to time, a person who needs bifocal lenses must use the high magnification area of the lenses while viewing in a body position which may be quite different from that for reading. For example, repair technicians, building mechanics, and others who perform manual tasks must from time to time work in areas that are obstructed to direct access, or access which would be easily viewed if the person had perfect vision. Because the eyes must align in a particular way, it may be necessary for people who are working in tight quarters, or who must look upwardly to perform a particular task, to have to hold their heads in unnatural and awkward orientations in order to utilize the relatively small area or zone of bifocal lenses which provide relatively great magnification. Illustratively, a person may need to tilt his or her head backwardly to a great extent so that the line of sight passes through the high magnification zone while looking in an upward direction.
Holding the head in this unnatural and awkward position can cause muscle strain and other objectionable consequences, so that the task can become difficult and unpleasant if not entirely impossible.
The prior art has a need for increasing versatility of bifocal type glasses to ameliorate the unnatural and awkward body positions which are occasionally necessary given today's glasses configurations.